1. Field of the Invention
This invention relates generally to axles, wheels and suspensions for vehicles. More specifically, this invention relates to a drop-down extra axle and wheel set for a utility truck, like a pick-up truck, for example, when extra support is needed for additional load on the truck.
2. Related Art
U.S. Pat. No. 3,743,315 (Bilas) discloses an extra axle and wheel set for a trailer. The extra axle and wheel set are urged up off the roadway from a pivot bracket on the main frame of the trailer by a semi-elliptical spring positioned transversely of the vehicle longitudinal axis. The extra axle and wheel set are urged down on the roadway by a set of air bags.
U.S. Pat. No. 4,146,243 (Sims) discloses an extra axle and wheel set for the rear of a cement truck. The extra axle and wheel set are urged up and down, off and on the roadway, respectively, by a set of air bags. A hydraulic ram device on each wheel further lifts the extra axle and wheel set up into a transport position.
U.S. Pat. No. 4,705,133 (Christenson, et al.) also discloses an extra axle and wheel set for a cement truck. The extra axle and wheel set pivots up and forwardly from a point on the rear end of the main frame to be lifted off the roadway by a hydraulic ram. In the lifted position, the extra axle and wheel set straddles the rear end of the truck frame.
U.S. Pat. No. 5,370,196 (Bishop) discloses an extra axle and wheel set for a vehicle. The extra axle and wheel set pivotally attach to a bracket which is bolted to the rear part of the frame of the vehicle. The extra axle and wheel set is lifted off the roadway by a hydraulic ram.
Still, there is a need for a simple, strong and economical drop-down extra axle and wheel set for a truck. This invention addresses that need.